In the process of shipping an item from one location to another, a protective packaging material is typically placed in the shipping case, or box, to fill any voids and/or to cushion the item during the shipping process. Some conventional protective packaging materials are plastic foam peanuts and plastic bubble pack. While these conventional plastic materials seem to adequately perform as cushioning products, they are not without disadvantages. Perhaps the most serious drawback of plastic bubble wrap and/or plastic foam peanuts is their effect on our environment. Quite simply, these plastic packaging materials are not biodegradable and thus they cannot avoid further multiplying our planet's already critical waste disposal problems. The non-biodegradability of these packaging materials has become increasingly important in light of many industries adopting more progressive policies in terms of environmental responsibility.
The foregoing and other disadvantages of conventional plastic packaging materials have made paper protective packaging material a very popular alterative. Paper is biodegradable, recyclable and composed of a renewable resource, making it an environmentally responsible choice for conscientious industries.
While paper in sheet form could possibly be used as a protective packaging material, it is usually preferable to convert the sheets of paper into a relatively low density pad-like cushioning dunnage product. This conversion may be accomplished by a cushioning conversion machine/method, such as those disclosed in U.S. Pat. Nos. 3,509,798, 3,603,216, 3,655,500, 3,779,039, 4,026,198, 4,109,040, 4,717,613 and 4,750,896, and also in pending U.S. patent applications Ser. Nos. 07/533,755, 07/538,181, 07/592,572, 07/734,512, 07/786,573, 07/840,306 and 07/861,225.
With most, if not all, of the conversion machines/methods disclosed in the above-identified patents and applications, the cushioning product is produced by converting multi-layer, and preferably three-layer, paper stock material into a desired geometry. The cushioning product includes pillow-like portions formed by the lateral edges of all of the layers of stock paper being rolled inwardly to form a pair of twin spirals. The central regions of this structure are then compressed and connected (such as by coining) to form a central compressed portion and two lateral pillow-like portions which essentially account for the cushioning qualities of the product.
The central compressed portion of such a cushioning product is believed to be necessary to ensure that the pillow-like portions optimally maintain their cushioning qualities. In other words, without a connection of this type, the resiliency of the pillow-like portions would encourage the twin spirals to "unwind." However, the central portion, due to its compressed state, increases the density of the overall cushioning product.
The cushioning conversion machines disclosed in the above-identified patents use a connecting assembly comprising a pair of loosely meshed gear-like members between which overlapping portions of the stock material layers pass. The loosely meshed gear-like members cooperate to stitch, as by coining, the overlapping portions thereby to connect the strip along the central portion of the product disposed between lateral pillow-like portions that primarily contribute to the cushioning properties of the product.
A secure stitching is desired to maintain the intactness of the pillow-like portions and thus the cushioning properties of the dunnage product. To this end, perforations heretofore have been provided in the connecting portion of the produced dunnage strip to aid the coined portions in preventing opening up or separation of the connected portions of the product, this commonly being referred to as "unzippering". The perforations were produced by projections extending radially outwardly from the teeth of at least one of the gear-like members. For further details, reference may be had to U.S. Pat. Nos. 4,937,131 and 4,968,291.
Although the connecting assemblies disclosed in the above-identified patents adequately perform their connecting and other functions, it would be desirable to have a stitching assembly that further facilitates and/or enhances the stitching of overlapped portions of sheet-like stock material forming a low density cushioning product, particularly when using heavier weight and/or stiffer stock material.